10000426 
Message
Enter tax code subject to purchasing postings
Diagnosis
You have opened the Posting Templates window and have selected the Automatic VAT checkbox. You have defined a tax code, and have chosen the Add button. In the Tax Posting Account field, you have specified Purchasing Tax Account, but in the Tax Code field, you have specified a tax code not subject to purchasing postings.
Procedure
In the Tax Code field, specify a different tax code that is subject to purchasing postings.